This invention relates to the field of methods and devices for phototherapy. More particularly, the invention relates to methods and devices for treating and preventing circadian rhythm disorders such as seasonal affective disorder (SAD), jet lag, and related conditions using light emitting diodes (LED""s).
Circadian rhythms are physiological and behavioral oscillations that are normally synchronized with the natural light-dark cycle of the day. Circadian rhythm disorders are inappropriate or undesired circadian rhythms. Such disorders typically are related to sudden and/or extreme changes in the relationship between an organism""s exposure to environmental light and its activity. For example, circadian rhythm disorders are known to be associated with change in geographical location (jet lag) and night activity (graveyard shift workers). Another common type of circadian rhythm disorder is seasonal affective disorder (SAD), which is characterized by symptoms such as depression during the winter seasons when the duration of daylight is reduced.
It has long been known that circadian rhythms in humans and other mammals are affected by exposure of the retina to light. Accordingly, various techniques and devices have been developed to treat circadian rhythm disorders by exposing the eyes to light.
In U.S. Pat. No. 4,858,609 Cole discloses a bright light mask for shining high intensity light into a subject""s eyes at preselected time periods to modify circadian rhythms, even while the subject is asleep. Light from an incandescent bulb or a bank of green LED""s is delivered through optical fibers to the mask, providing to the eyes an intensity of at least 2000 lux and a wavelength in the range of 500 to 600 nm. A computer controller determines the intensity and timing of the light. The device of Cole, however, is not portable, blocks the subjects vision, and is expensive.
Czeisler et al. in U.S. Pat. No. 5,163,426 disclose techniques for assessing and adjusting circadian phase using goggle-like devices, powered by an external power supply. The goggles expose the retinas of a subject to high intensity light generated by fluorescent or incandescent lamps positioned near the eyes The goggles, however, interfere with normal vision, are not completely portable, are expensive, and are fragile.
In U.S. Pat. No. 5,503,637 Kyricos et al. disclose a portable apparatus for producing and delivering high-intensity white light to the eyes in order to modify the subject""s circadian phase. The apparatus is shown in the form of a sports visor having a high intensity cold cathode fluorescent lamp imbedded in the underside The light is filtered so that unwanted frequencies of light are not radiated to the subject""s face. A controller is provided which is programmed to deliver an amount of light determined to treat a circadian rhythm disorder. The apparatus, however, is fragile, bulky, expensive, and cannot be used while asleep, with eyes closed, or without attracting attention.
In U.S. Pat. No. 4,911,166 Leighton et al. disclose a device for delivering high intensity light to a patient""s eyes for treating SAD and the like. It has a high intensity halogen or other incandescent bulb, with reflective optics to direct a large portion of the light directly into the subject""s eyes. The light source is fixed to a head-mounted apparatus. The apparatus, however, is fragile, bulky, interferes with normal vision, and cannot be used without attracting attention.
Known techniques for treating circadian rhythm disorders, therefore, suffer from one or more of the following disadvantages: they are expensive, fragile, bulky, not portable, energy inefficient, emit unwanted heat and/or radiation, interfere with normal vision, and may attract undesired attention from others. It should be emphasized that all these devices for treating circadian rhythm disorders are based on the exposure of the retina to light, usually broad spectrum (white) light.
In the article xe2x80x9cExtraocular Circadian Phototransductionxe2x80x9d (Science, Vol. 279, Jan. 16, 1998) Scott S. Campbell and Patricia J. Murphy teach that circadian rhythms can be altered by illuminating the popliteal area of each leg (i.e., the area behind the knee). Campbell and Murphy use a commercially available device which has a halogen lamp in a metal housing with a fan to dissipate heat. A collection of 2400 optical fibers are used to deliver the light from the housing to a 10 cmxc3x9715 cmxc3x970.5 cm pad. The pad is held in place behind the knee by a polyester athletic knee brace for 3 hours. The wavelength of the light delivered to the subject by the device is in the 455 nm to 540 nm range, i.e. blue-green light. They also teach the use of white light from a fluorescent lamp. This device, So however, has several disadvantages: it is not portable, it is awkward, it generates considerable heat and noise, it consumes considerable power, and is very expensive. In addition, their use of the popliteal area interferes with normal activity and comfort since it limits the bending of the knee.
In view of the above, it is an object of the present invention to provide a device for effectively treating circadian rhythm disorders that is inexpensive, portable, durable, compact, light-weight, energy efficient, does not generate undesired heat or radiation, does not interfere with normal vision, and inconspicuous. It is another object of the present invention to provide a device for treating circadian rhythm disorders that may be used while the subject is asleep as well as awake.
Another object of the invention is to provide such a device having precise control and delivery of specific wavelengths and intensities of light to the subject.
The above objects and advantages are achieved through the use of devices that deliver light to a subject""s retinas, to the subject""s vascular tissue, or simultaneously to both the retinas and the vascular tissue. The vascular tissue is typically the vascular bed underlying the skin. The portable devices employ one or more LED""s for directly illuminating the retinas and/or vascular tissue of the subject. The LED""s may be single LED""s, LED arrays, or integrated array LED chips. For illumination of the retina, one or more small LED""s are placed into the frames of eyeglasses and positioned to direct light into the eyes of the subject. For illumination of the vascular tissue, an array of LED""s are contained in a casing that is secured against the skin of the subject. The devices are preferably powered by separate batteries. Alternatively the devices can be powered by a common battery supply. The devices can be used independently of each other, or can be used in conjunction for more effective and/or flexible treatment. In a preferred embodiment, the intensity, timing, and wavelengths of light delivered by the devices is easily adjusted by controls on the device. wavelength selectivity provides fine-tuning of the most appropriate treatment for the condition of the subject.
In one aspect of the invention, a device is provided for treating a circadian rhythm disorder in a subject. The device comprises one or more light emitting diodes (LED""s), preferably blue to green in color; a mounting to which the LED""s are connected; a material for positioning the LED""s within 3 cm of the subject, with an orientation toward the subject; a portable power supply electrically connected to the LED""s; and a control connected to the LED""s for altering the operation of the LED""s. The device is sufficiently light and compact to be comfortably worn by the subject. In one embodiment, the material for positioning the LED""s within 3 cm of the subject comprises eyeglass frames and arms, and the LED""s are oriented toward the eyes of the subject. In another embodiment, the material for positioning the LED""s within 3 cm of the subject comprises a fabric that may be wrapped around a portion of the subject, and the LED""s are oriented toward the skin of the subject. The device may also include an integrated circuit for controlling the LED""s.
In another aspect of the invention, a method is provided for treating circadian rhythm disorders experienced by a subject. The method comprises illuminating the subject with light produced by a portable device worn by the subject. The device comprises a plurality of light emitting diodes (LED""s) positioned within 3 cm of the subject for illuminating the subject, a power supply connected to the LED""s, and a control connected to the LED""s. The method may further comprise simultaneously illuminating the subject with light produced by an additional device worn by the subject. The devices may illuminate the eyes of the subject, the vascular tissue of the subject, or both. To illuminate the eyes, the device is worn on the face of the subject. To illuminate the vascular tissue, the device is worn on a portion of the subject""s body, such as the head, neck, arm, waist or leg. Although multiple wavelengths may be used, preferably, the light produced by the LED""s and used to illuminate the subject has a narrow spectral content in the blue to green portion of the spectrum.